The Fyreye MKII multi-detector uses a Rate of Rise AR1 element that uses a thermistor arrangement to sense a quick rise in temperature and a final threshold temperature of 57°C.

The Fyreye MKII multi-detector also uses a smoke sensing element that uses a pulsing IR LED & photodiode to detect IR scatter caused by smoke entering the chamber.

The detector is particularly suitable for detecting optically dense smoke, involving materials such as soft furnishings, PVC, plastic, foam and all similar materials which produce small visible particles (0.5 to 10?m).